What kind of pipe for water feeder

DanT

I just bought a house and the boiler (1976 but newer external parts) has a lot of problems.  I noticed the water feeder has a partial run of black pipe and the threaded elbows are completely rusted. 



It really looks like someone just used gas pipe. Should I replace this with sweated copper?  It looks to be 3/4 inch.  



You can see the black pipe at the top of the picture:

Charlie from wmass

Iron is "ok" after the feeder

I use copper up to a brass nipple where I enter the return. But looking at the photo those burn marks are saying the boiler has bigger issues. Like the flames not venting properly up the chimney. If you do not have a CO detector you should get one. Gas pipe and steam pipe are the same pipe. the fittings differ as cast iron is used traditionally for steam and malleable only is used for gas as per gas code.